Abstract
A study was conducted to determine whether temperature influences the nature of organic matter transformation in low-permeable rock of the Mendym deposits Upper Devonian of the Tavel oil field (Tatarstan). An experiment was conducted at 250°C, 300°C, and 350°C in a carbon dioxide environment with a 1:1 water to rock ratio and an exposure time of 24 hours in a carbon dioxide environment. The degree of kerogen conversion in the rock was determined, changes in the composition of the formed gases, group and hydrocarbon composition were assessed extracts (composed of saturated and aromatic hydrocarbons) from the rock before and after hydrothermal experiments. It was established that under these experimental conditions at a temperature of 250°C, a decrease in the content of saturated hydrocarbons and an increase in asphaltenes is observed in the extract composition, which indicates the process of desorption of asphaltenes from the kerogen surface and extraction of free hydrocarbons from the rock. At a temperature of 300°C, the yield of the extract increases slightly, however, as a result of the destruction of kerogen and high-molecular components (mainly resins), new hydrocarbons are formed, the content of saturated hydrocarbons increases from 14.53 to 27.34% compared to the original extract. The greatest changes in the composition of gaseous products and extract occur at 350°C, which is reflected in the almost complete extraction of hydrocarbons from the rock, the greatest increase in the yield of hydrocarbon and inorganic gases, and an increase in the content of light hydrocarbons in the composition of the extracts obtained. The content of saturated hydrocarbons increases to 35.29%, aromatic hydrocarbons from 23.11 to 31.11%, while the asphaltenes content decreases by more than 2.5 times. According to the molecular weight distribution data of aromatic hydrocarbons, it has been established that the transformation of organic matter at 350°C is most accompanied by the separation of di-, tricyclic and heterocyclic sulfur-containing aromatic fragments from polycondensed structures.
Published Version
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